EARTHQUAKE-RELATED PERFORMANCE LOSSES OF SOLAR POWER PLANTS

Solar power plants are subject to numerous unpredictable risks during earthquakes, resulting in damage that can be characterised as an attached risk. It is anticipated that severe earthquakes will have similar impacts on all solar power plants in the affected region due to the physical changes they trigger. In addition to the direct physical damage to panels and supporting structures caused by the earthquake, secondary risk factors such as changes in panel placement angle and reduced radiation time due to mass ground movement or sinking can result in functional problems. Furthermore, micro-cracks on the panels that may not be immediately visible can result in a loss of overall production performance.

For solar power systems to operate efficiently throughout the year, it is critical that the direction and angle of the solar panels are properly selected for the location. In the northern hemisphere, where our country is located, solar panels are typically oriented towards the south. The angle of inclination for solar panels varies depending on the location of the system.

Various methods can be used to calculate the optimal angle of inclination for maximum solar power utilisation throughout the year. One approach is to use formulas to convert the location’s latitude value into the necessary angle of inclination.

Turkey is situated between 36-42° North latitude and 26-45° East longitude. Latitude refers to a location’s distance from the equator, and each city in our country has a different latitude value. As a result, the optimal angle of inclination for solar panels will vary from city to city.

Within our country’s borders, depending on where the solar panel will be installed, the optimal angle of inclination ranges from 35 to 40 degrees.

The table below provides calculations for provinces in earthquake zones that use a fixed panel inclination angle throughout the year. The third column of the table displays the city’s latitude value, while the fourth displays the recommended inclination angle for use in calculations.

After the Kahramanmaraş, Pazarcık earthquake on February 6th, research and satellite imagery revealed that the Anatolian plate had shifted by 3 meters, resulting in changes to latitude values. As a result, the angles at which solar panels can operate efficiently have changed, and it is expected that performance losses in solar power plants in the region will deviate from installation data and increase.

STRUCTURAL EFFECTS OF EARTHQUAKE ON SOLAR POWER PLANTS

Engineering and Catastrophic Risk Department of Ekol Loss Adjusting has been conducting observational and experimental studies in the field since February 7th to assess the structural effects of earthquakes on solar power plants.

Possible types of losses following an earthquake include;

• Performance losses due to changes in panel placement angle caused by landslides,
• Losses that may occur due to deformations in power cables in the system infrastructure,
• Performance losses due to micro-cracks on solar panels caused by stretching during an earthquake.

In addition to observable physical material losses, these effects can result in increased performance losses as an indirect result of earthquakes.

1- Deformations on the Power Plant Site Ground
Examinations of the ground at solar power plant sites revealed deformations such as sliding and cracking / separation in certain areas.

2- Deformations Occurring Carrier Systems

During field examinations, structural deformations were observed in the equipment supporting solar panels due to ground movements.

3- Deformations in Power Plant Power Infrastructure

Transformers located in kiosk buildings slipped from their pedestals and openings were observed within the structure of the kiosk building itself.

4- Micro Cracks that May Occur on Solar Panels Due to Earthquake

• Micro cracks are small, difficult-to-detect cracks that can form on panels. These cracks can occur when panels fixed to a structure are subjected to movement beyond their stretching ability due to ground movement during an earthquake.

• Although these cracks may not have an immediate impact, performance losses will occur over time as the cracks grow in size and reduce the efficiency of the solar panels. Hotspot formation on solar panels can occur as a result of an earthquake, as well as for other reasons including:

– Micro cracks or fractures caused by physical impact during installation,
– Moisture,
– Corrosion,
– Seasonal temperature changes,
– Precipitation,
– Micro cracks non-visible to eye caused by wind-blown debris such as pumice stones hitting the panels,
– Shading,
– Snail trails.

Hotspot Formation, Its Impact on Energy Production and Methods of Detection

Photovoltaic solar panels are one of the most important components of solar power plant production elements. These panels are composed of a series of interconnected cells. Because these cells are connected in series, the current produced by the series cells (according to Kirchhoff’s current law) flows through all the panels in the series in equal amounts. If one cell produces less current than the other cells, it will create a reverse voltage in that cell and instead of producing the expected electrical energy, the energy will be converted into heat due to a power imbalance. This will result in the cell heating up, and, over time, the formation of a hotspot due to an increase in heat in the affected photovoltaic panel.

Since solar power plants are composed of panels connected in series, a hotspot problem not only affects that panel but also impacts other string groups in plants where string inverters are used, resulting in significant changes in production.

To determine if damage to solar panels is due to an earthquake, it is expected that micro cracks formed on solar panels will affect all solar panels on the same carrier system without being independent of different points on the same table/row.

Performance Control and Measurement Methods in Solar Power Plants

The performance of solar power plants can be controlled and measured by conducting tests within the scope of IEC62446 and IEC60891. These tests include IV-curve (current-voltage) measurement, thermal tests with drones, EL (electroluminescence) test, grounding test, insulation test, and performance measurement.

A- IV- Curve Measurement

As shown in the IV Curve measurement below, problems such as LID (Light induced degradation), PID (Potential induced degradation), and micro-crack degradation can be detected in all solar panel arrays in the field by extracting their IV measurements. These measurements also serve as a record and enable the determination of the degree of degradation (normal loss) of the solar panels in future controls.

The IV curve test can provide information on the following issues:
• The actual power of solar panels, LID-related losses on solar panels,
• PID,
• Ground contact or leakage due to cuts or rodent bites on DC cables,
• Problems with the by-pass diodes of solar panels,
• Detection of shading-related problems,
• Possible faulty connections in panel series.

B- Hotspot Measurement with Drone and Handheld Thermal Imager

Hotspots can occur after solar panels are commissioned. This control can be performed using either a thermal drone or a handheld thermal imaging device. Thermal monitoring and control is important for detecting hotspots in solar power plants.

Thermal measurement can provide information on the following issues:

• Damaged cells on solar panels,
• Unexpected heating in panel materials such as by-pass diodes and junction boxes,
• Environmental factors causing shading,
• Arrays that have never been commissioned

C- EL (Electroluminescence) Test of Solar Panels

The EL photograph of solar panels can be considered as an x-ray for future potential problems. It can determine if cells were damaged during manufacturing or installation stages.

Measurement can provide information on the following issues:
• Cell structure,
• Whether there are breaks in the cells,
• The effects of carrying over-head during SPP installation or if the panels have been forced.

D- Insulation (Hipot) Tests
The insulation resistance between the panel and the ground is checked by applying a 1,000-volt DC voltage to the solar panels. This is important for preventing leakage in the panels and protecting people, as well as for preventing damage to inverters. Damage during SPP installation can be detected at this stage.

Measurement can provide information on the following issues:
• Whether there is any damage to the cables,
• Whether there is a phase-ground fault in the DC voltage part of solar panels,
• Whether there is a problem affecting insulation resistance that will disable inverters.

E- Grounding Value Measurement
Grounding measurement is important in all power generation and consumption facilities, especially solar power plants. Grounding is important for real leakage current protection and general protection, particularly against lightning strikes near the plant. A break in grounding or equipotential bar can cause serious damage to the system. In this context, both the grounding measurement of the equipotential bar with megger and the grounding measurement of the construction and solar panels should be recorded and necessary measures taken if a problem is detected.

F- PVSYST Simulation Using Real Values

A simulation is performed using PAN files provided by the panel manufacturer based on radiation and panel temperature data recorded by the plant. The energy to be produced is calculated and compared with the energy actually produced. These results are used to determine if there are any overlooked issues in the system (such as transformer or inverter losses) and to create a general production expectation profile. This test checks for problems in the system as a whole. With this calculation, solar power plant performance measurement is performed and the performance value of the power plant is determined.

Simulation can provide information on the following issues:

• The amount of energy that should be produced by the plant according to the data,
• Whether the performance measurement of the power plant is accurate,
• How much performance the power plant produces.

Currently, there may be multiple factors that can affect performance in solar power plants, and these factors can be detected by applying different methods mentioned above.

5- Dust Contamination

According to information from the dust transport warning system provided by the General Directorate of Meteorology, a dense dust cloud was present in the region following the Kahramanmaraş, Pazarcık earthquake. The impact of dust clouds on solar panels is expected to result in significant performance losses in solar power plants in the region.

When all these issues are considered, it is clear that the earthquake had an impact on the performance of solar power plants. Research has shown that the earthquake occurred on the Eastern Anatolian fault line between the northern Anatolian plate and the southern Arabian plate. As a result of the Anatolian block moving approximately 3 meters to the west, changes in radiation due to changes in panel placement angle and radiation are expected to result in decreased production values in solar power plants. In any case, the impact of the earthquake will become clearer with statistics on production data obtained during the ongoing process in the general region.

6- The Effect of Earthquake on Solar Power Plants Installed on Building Roofs

Many buildings were affected by the earthquake disaster on February 6th, 2023. Many factories, businesses, and facilities located in the provinces affected by the earthquake have solar power plants installed on their roofs and engage in energy production activities. Due to the earthquake, many of these structures collapsed or suffered heavy damage, resulting in corresponding damage to roof-mounted solar power plants due to the collapse mechanism of the structure. Examination of these types of damages revealed that many solar power plants were partially damaged.

On the other hand, examination in the general region revealed that static reinforcements were not made when roof-mounted Solar Power Plants were installed with licenses obtained later for operating structures. Since the load of the solar power plant is not included in the building’s design, it is not taken into account. When the decision to install a SPP on the roof is made after the building has been completed and used for a certain period of time, SPP load calculations must be performed and the roof and building support systems must be reinforced accordingly. It was determined that reinforcement calculations were not performed in none of the examined roof-mounted solar power plants and that damage to support systems increased due to the extra load effect at the junction points of trusses / columns in standard industrial-type prefabricated reinforced concrete support buildings. While it is possible to prevent negative effects with extra safety measures and reinforcements in rigidly connected span areas, both structural and plant damage occur due to the lack of relevant reinforcement calculations.

7- Another type of loss resulting from the earthquake is the inability to transfer energy produced to the grid due to damage sustained by the regional distribution company

Due to the earthquake risk, there was no electricity distribution activity for a certain period in the grid of the regional electricity distribution company. As a result, inverters in solar power plants without physical damage did not operate because there was no electrical energy in the distribution network, resulting in the problem of not being able to transfer energy produced on panels to the grid.

8- The Importance of Ground Survey and Earthquake Load

Data obtained from ground survey reports are used in determining earthquake load. Therefore, it is important that ground survey studies are conducted with a sufficient number of research pits and drilling studies to accurately reflect the ground characteristics of the field. However, ground survey studies conducted with only a few (usually a single) samples on a wide area in almost all power plant projects generally do not accurately reflect the overall structure of the site. One frequently encountered type of damage occurs when support columns sink into soft ground under minimum loads.

When examining ground surveys, investors or risk engineers should pay attention to determining if there are filled areas by comparing the current situation with the situation of the site a few years ago, if available, and recommend increasing the number of research its and drilling throughout the site. Soft ground that may not be detected during ground surveys can easily be noticed during the installation phase. Therefore, if support columns can easily be driven by controllers during installation, it must be reported to the relevant units. In these areas, measures such as driving the support column deeper or injecting concrete should be taken and pull tests should be frequently applied after manufacturing throughout the site.

Even under normal conditions, inadequacies in site-ground structure analysis practices are striking and their importance increases in post-earthquake situations.

For example, in a standard static calculation report, appropriate earthquake parameters are used according to the location of the Solar Power Plant when making design calculations. Data obtained from the ground survey report are also taken into account and factors such as ground class, earthquake zone, altitude, building importance coefficient (I), support system coefficients (Rx/Ry), and earthquake acceleration coefficient (Ao) are determined. The support structure and foundation elements are designed using these coefficients.

Insufficient or incorrect ground survey studies can result in damage mechanisms such as ground slip/break/flow/landslide on sloping lands due to earthquake risk in solar plants where no visible problems can be detected.

When making static calculations, data obtained from the ground survey are used as shown below.

Ground Values,
-Ground Class,
-Ground Safety Stress,
-Vertical Bearing Coefficient,
-Horizontal Bearing Coefficient,
-Horizontal Spring Coefficient,
-X, Y Direction

The impact of an earthquake varies depending on the location. Two different power plants located in the same province but in different districts and at different altitudes can experience very different damage mechanisms. Even the extent of the damage can vary depending on the quality of the materials used and the workmanship applied in the foundation and construction manufacturing based on static calculations. Many factors such as the dimensions of the profiles used, the intervals at which they are mounted, the type of bolt used, and whether aluminium or steel is used are evaluated. However, workmanship is important in the final outcome. Even if power plant structures are perfectly designed statically, if the workmanship is incomplete or incorrect, the first manufactured elements will not be long-lasting and will not provide sufficient resistance to natural disasters.

In general terms, the impact of an earthquake is catastrophic and contains many variables such as frequency, duration, depth, oscillation, wavelength, soil type, etc. However, it is important for insured parties and shareholders to properly utilise necessary engineering services and related scientific fields before installation and to design for an optimal earthquake impact. Since these documents are examined in detail during the preparation of a survey report, consistency between design and application is a critical control point.

In our examinations following an earthquake risk, it was determined that while complete collapse and plastic shape changes occurred in some power plants due to the earthquake, micro-cracks, slips, and displacements that were not visible to the naked eye occurred in some construction elements in other power plants. Although these deformations do not hinder energy production by the power plant, claims for production loss arise due to repairs of deformations.

In some cases, no damage occurs to foundation or construction elements supporting the energy panels but various damages occur to solar energy modules While this can be attributed to many reasons or external factors, according to our general approach and damage experiences, panels have a higher resistance than construction in terms of carrying/transferring load falling on one area/capacity to show resistance. This approach is evaluated in damages related to external factors other than earthquakes. However, since the impact of earthquakes on buildings and power plants is greater and more catastrophic than other external factors (such as storms/snow loads/ice loads/floods & landslides etc.), it contains many variable.

In conclusion, it is expected that total collapse and bending / buckling / breaking / various plastic deformations in construction elements or collective damage mechanisms in foot concretes will occur in natural disasters including earthquakes. Catastrophic damage cannot be mentioned for the type of damage affecting separate units on different fronts of the power plant.

Considering all these reasons, it is important to report the current site situation to insurance companies with clarity after an earthquake. Since these notifications are mandatory to protect the rights of both the insured and the insurer, the most effective use of insurance policies will be achieved for all parties.

References:

 Ekol Loss Adjusting Risk & Claims Archive ( Eren Dursun )
 Solarian Enerji A.Ş. Articles
 General Directorate of Meteorology Datas

*** This bulletin has been prepared based on our experiences in the field of claims and risk with information compiled from various sources related to the subject and contains our own views.